Knife sharpener



FIG. 1 is a perspective view of a knife sharpener embodying my design;

FIG. 2 is a front elevational view thereof; the rear elevational view being a mirror image thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a right elevational view thereof, the left elevational view being a mirror image thereof.

The dashed lines in FIGS. 1 and 5 illustrate environment only and form no part of the claimed design. 

The ornamental design for a knife sharpener, as shown and described. 